The present invention relates to reducing the harmonic noise generated by the propulsion motor control chopper apparatus of one or more transit vehicles in relation to receiving the input control signal frequencies, such as are provided for a vehicle detection and for speed control within predetermined track signal blocks, as described in an article published in the Westinghouse Engineer for September, 1972 at pages 145 to 151.
Both the train vehicle traction power system and the train vehicle control and protection system use the running rails as electrical conductors. The ground return current path for heavy rail and light rail transit vehicle systems is one or both of the running rails. The rails are also divided into regions called signal blocks by the train control and protection system for the provision of circulating signal currents in the running rails. These signal currents are used to detect the presence of the train vehicle in a block section of track and in some systems to provide the train vehicle with the safe speed to proceed information. The signals in the running rails are used to avoid rear end collisions, head-on collisions, excessive speed in turns and to allow safe passage through switches. If the traction power system produces electromagnetic interference or EMI that conflicts with the train control and protection system signals, then vehicle safety and reliability problems can occur. It is desired to provide a control technique for a vehicle carried DC motor controlled chopper apparatus that greatly increases the signal level margin between the undesired EMI signal level produced by the chopper and the signal response threshold of the train control and protection system.
It is known in the prior art, as disclosed by U.S. Pat. No. 4,282,466 to provide a programmed microprocessor control apparatus coupled with a chopper apparatus for controlling a vehicle propulsion motor to determine the operation of that motor, and the disclosure of this patent is incorporated herein by reference.